It is effective to reduce the dimensions of field effect transistors, for enhancing the packaging density and driving capabilities thereof. In recent years, therefore, the microfabrication of the field effect transistors has been rapidly promoted. On the other hand, however, a supply voltage to each of the field effect transistors remains constant, and hence, the intensity of an electric field within the element increases. This has resulted in the occurrence of problems exerting bad influences on the characteristics of the element, such as a short channel effect. The short channel effect is a phenomenon in which, due to reduction in the channel length of the field effect transistor, the drain voltage of the transistor affects even a part lying directly under the gate electrode thereof, so that the potential of the surface of a semiconductor substrate is lowered to incur various evil effects such as fluctuation (fall) in the threshold voltage of the transistor and decrease in the effective channel length thereof. When the short channel effect has intensified more, so-called "punch-through" in which the drain current of the transistor fails to be controlled by the gate voltage thereof takes place to pose the problem of increase in the leakage current between the source and drain of the transistor. It has been known that the punch-through gives rise to degradation in the retention of storage in, for example, the transfer gate of a DRAM (Dynamic Random Access Memory). A technique which has been studied for avoiding the problems is, for example, one wherein in order to suppress the short channel effect, heavily-doped semiconductor regions (hereinbelow, termed "pocket regions") of the same conductivity type as that of the impurity of the channel of a field effect transistor are provided at those end parts of the source region and drain region of the transistor which are near to the channel. Incidentally, a technique for providing the pocket regions is stated in, for example, U.S. Pat. No. 5,780,328.